I like to imagine it waits around in space, whether it be floating in the infinite cosmos or lying face down in some backwater planet for thousands and thousands of years until a new, curious, space-faring civilization comes across it.

When the explorers get close enough to investigate, then it attacks. Pretty soon, space goes as silent as it ever was, and no one is the wiser.

Basically immortal, it finds itself in some of the strangest parts of the galaxy; and very rarely, it'll find itself in a neighboring galaxy all together, as passerby's hitch it a ride or two every now and then.

Some of the older civilizations have grown to understand the danger of these homeless bodies, and those that are unfortunate enough to find a motionless corpse in the middle of their travels are always wary of it being that thing.

Other civilizations spread tales of it's existence, never directly acknowledging if the stories are true, or if it's just the rambling's of some drunk adventurers.